NAME¶

std::ranges::view_interface::back - std::ranges::view_interface::back

Synopsis¶

constexpr decltype(auto) back()
requires ranges::bidirectional_range<D> && (1) (since C++20)
ranges::common_range<D>;
constexpr decltype(auto) back() const
requires ranges::bidirectional_range<const D> && (2) (since C++20)
ranges::common_range<const D>;

The default implementation of back() member function returns the last element in the
view of the derived type. Whether the element is returned by value or by reference
depends on the operator* of the iterator type.

1) Let derived be static_cast<D&>(*this). Equivalent to return
*ranges::prev(ranges::end(derived));. The behavior is undefined if empty() is true
(i.e. the beginning iterator compares equal to the sentinel), even if the iterator
obtained in the same way is dereferenceable.
2) Same as (1), except that derived is static_cast<const D&>(*this).

Parameters¶

(none)

Return value¶

The last element in the view.

Notes¶

In C++20, no type derived from std::ranges::view_interface in the standard library
provides their own back() member function.

However, following derived types cannot use the default implementations, as they
never satisfy neither bidirectional_range nor common_range:

* std::ranges::basic_istream_view
* std::ranges::lazy_split_view
* std::ranges::split_view
* std::ranges::take_while_view

The inherited back() member function is available for std::ranges::empty_view, but a
call to it always results in undefined behavior.

Example¶

This section is incomplete
Reason: no example

See also¶

rbegin returns a reverse iterator to the beginning of a container or array
crbegin (function template)
(C++14)
ranges::rbegin returns a reverse iterator to a range
(C++20) (customization point object)
ranges::crbegin returns a reverse iterator to a read-only range
(C++20) (customization point object)

Category:¶

* Todo no example